The present invention relates generally to wireless communication systems, and more particularly, to a method and an apparatus for controlling mobile access to a wireless communication system.
A wireless communication system is a complex network of systems and elements. Typical elements include (1) a radio link to the mobile stations (e.g., cellular telephones), which is usually provided by at least one and typically several base stations, (2) communication links between the base stations, (3) a controller, typically one or more base station controllers or centralized base station controllers (BSC/CBSC), to control communication between and to manage the operation and interaction of the base stations, (4) a call controller or switch, typically a mobile switching center (MSC), for routing calls within the system, and (5) a link to the land line or public switch telephone network (PSTN), which is usually also provided by the MSC.
In a wireless communication system, a mobile station typically communicates to a base station over several communication channels, e.g., a control channel, a traffic channel, and an access channel. In particular, the mobile station uses the access channel to signal to the base station, via a mobile access message, a request to obtain communication services, i.e., to access the communication system. The mobile access message may be, but is not limited to, a registration, a data burst message, a page acknowledgment, and a call origination initiated by the mobile station that is transmitted via the access channel to the base station. However, only unsolicited mobile access messages, i.e., originated without prompting by the base station, may be controlled to access the communication system. Specifically, unsolicited mobile access messages include registrations, data burst messages, and call originations. A registration indicates the status of the mobile station, i.e., whether the mobile station is active or inactive, or the location of the mobile station, i.e., whether the mobile station has moved into a different sector within a communication cell. A data burst message includes a textual message which may be destined for another mobile station, to a pager or a MSC. A call origination is a request by the mobile station to initiate a voice or data call.
One aspect of designing wireless communication systems is to ensure a high level of access to the communication system by the mobile stations. It is especially important that mobile stations are able to access the communication system in critical situations or where the mobile stations are identified as having high priority. The communication system must also prevent such critical and high priority mobile stations from being indiscriminately denied access by base stations within the communication system when the base stations experience overload conditions.
In critical situations, such as an earthquake or any other type of natural disaster, a high volume of mobile access messages originated by mobile stations is quite natural. Accordingly, critical mobile access messages should have higher priority to access the communication system than other non-critical registrations, data burst messages, or call originations. For example, a voice call originated from a mobile station used by a fire fighter to request for more assistance should have higher priority than other non-critical mobile access messages. Other critical mobile access messages include access messages originated from mobile stations used for special purposes such as, but not limited to, system maintenance. However, current wireless communication systems indiscriminately deny mobile access to the communication system without taking either the source or the type of a mobile access message into consideration. Therefore, the call origination by the mobile station used by the fire fighter in the example above or a data burst message from a mobile station used for system maintenance may be indiscriminately denied access to current wireless communication systems.
Because the base station under overload conditions permits any mobile access up to the capacity of the communication system, regardless of the importance associated with the mobile access, non-critical mobile stations or access types may have access to the communication system over critical or high priority mobile stations or access types. Therefore, a need exists for a method and an apparatus for controlling mobile access to a communication system based upon the availability of system capacity, and prioritizing of the mobile stations and the access types seeking access to the communication system.